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The determination of the hardness of a mineral can be an important step toward its identification. Hardness is the resistance which the smooth surface of a mineral offers to being scratched. A diamond is the hardest of all substances and can only be scratched by another diamond.
Over a century ago, Friedrich Mohs made up a scale of hardness which is referred to as Moh's scale. It does not imply an exact hardness, but is set up so that any mineral can scratch all those beneath it in the scale, or can be scratched by those above it.
This kit includes all the minerals in the Moh's scale of hardness, except the diamond. Talc is the softest, so it is given the number 1. Diamond is the hardest, so it is given the number 10 (a diamond is not included with this kit). Quartz is often used as a division in the scale and all those above 7 are called hard minerals. The minerals in this kit are these:
- Talc
- Gypsum
- Calcite
- Fluorite
- Apatite
- Feldspar
- Quartz
- Beryl
- Corundum
Some very familiar objects can be used in conjunction with this scale. A fingernail has a hardness of 2.5, a copper coin between3 and 4, a nail about 5, common window glass 5.5, a steel file or pocelain tile 6.5. This kit includes a nail, a glass streak plate, a white porcelain streak plate, and a penny for your hardness tests.
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